Materials used to reduce or eliminate the passage of smoke and flames through openings between walls and floors and the openings caused by through penetrations in buildings are known as fire stop, fire retardant, or fire barrier materials.
Intumescent sheets, caulks, putties, and coatings are known for use in various fire retardant or fire barrier applications. Many of these materials have a high organic content. In particular, intumescent compounds have been used with polymeric binders to form caulks for use in filling joints. Elastomeric sheets containing intumescent compounds are also known for use in pipe wraps or cable tray wraps.
Intumescent sheets which additionally contain a large inorganic component based on kaolinitic clay and other colloidal cementaceous materials typical of papermaking are also known. These clays and colloidal materials are considered to be inorganic binders by their nature. Characteristically, these binders results in stiff boardy articles which, like paper, must be formed in very thin layers to demonstrate any useful flexibility.
Non-intumescent non-char forming endothermic flexible sheet materials are also known which are essentially inorganic and are suitable for use in areas where electrical systems and sensitive equipment need fire protection. This type of sheet can have relatively high thermal conductivity in its unfired state.
In addition, compositions containing inorganic endothermic materials, such as sodium silicates, and intumescent materials in a free standing article in a sufficient quantity to provide swelling of a functional magnitude are known. Yet, in these compositions, typically, the remainder of the composition tends to consist largely of structural materials in the form of organic polymer combined with char forming additives, fibers, or stiff colloidal materials. Within another group of compositions with similar intumescent properties the remainder of the composition also typically consists of structural materials, but these compositions contain large amounts of fibers.
Thus, the industry is always seeking better and more effective materials. It is desired to provide a durable, freestanding, significantly intumescent heat absorptive fire barrier composition having a low combustible load and a high unfired density for low thermal resistance that will allow the useful dissipation of heat at room temperature. Such a material being especially useful in providing fire protection for electrical systems and sensitive electrical and mechanical equipment and generally useful as a non-combustible fire barrier which delivers a high heat absorptive value when used in small volumes. Such compositions would not depend on an organic char for their structural integrity in the fired state and would be especially useful in high temperature fires such as chemical fires or electric fires where organic chars are rapidly reduced to carbonaceous gases as well as in applications, for example, protecting electrical equipment and cables, where it is desirable to allow heat dissipation during normal operation and where inorganic fiber insulation is not useful. These compositions would be dense enough to provide, in relatively small amounts, the protection associated with substantial heat absorbing effects without a corresponding reduction in thermal conductivity of the system in the unfired state.